This is my presentation in plain English of St. Thomas’ arguments in Summa Theologiae,
secunda secunda, Question 2, Article 3.
Article 3 asks: In order to achieve salvation, is it necessary that we believe things beyond
natural reason, that is, by faith?
We have three good arguments for answering "no" to this question.
The first argument for answering “no” is:
Premise 1.
Salvation is the ultimate perfection of the human being.
Premise 2.
And the perfection of any natural thing should come through its natural abilities.
For example, a dog possesses by its nature all the abilities it needs to be a perfect dog.
It does not need to go beyond its canine nature to be perfected.
Premise 3.
But faith goes beyond the powers of reason (philosophy, science, etc.) that are part
of human nature.
Conclusion.
Therefore, faith is not needed for human perfection or salvation.
The second argument for answering “no” is:
Premise 1.
It is dangerous for anyone to believe what they do not understand.
Premise 2.
If you believe what you do not understand, you might easily believe something that is
actually false.
Premise 3.
But matters of faith cannot be clearly understood.
Conclusion.
Therefore, believing things on faith alone is dangerous, and not required for human perfection.
The third argument for answering “no” is:
Premise 1.
The Bible tells us that "the invisible things of God... are clearly seen."
Premise 2.
But whatever is clearly seen can be known, and does not have to be taken on faith.
Conclusion.
Therefore, it is not necessary for us to have faith to achieve salvation.
We also have one good argument for answering "Yes," faith is necessary:
Premise 1.
The Bible also tells us that "without faith it is impossible to please God."
Premise 2.
Obviously, pleasing God is necessary for salvation.
Conclusion.
Therefore, we must have faith in order to achieve salvation, or human perfection.
The key to this difficulty is realizing that when one nature is subordinate to another,
then the lower nature can be perfected in two ways, not just one way.
It can be perfected in relation to its own natural activities and powers.
It can also be perfected in relation to and by participation in the higher nature and
its powers.
For example, a pet dog has a canine nature that is also subordinate, in part, to the
human nature of its owner.
Therefore the dog has two types of perfection available to it.
First, the perfection of its own natural canine powers, on its own terms: running, hunting,
eating, etc.
Second, the perfection of its nature in relation to its owner's higher nature: obeying, playing,
guarding, etc.
Even though a dog's nature has all it needs to be perfect just as a dog, because it is
related to the higher, human nature of its owner, it has another level of perfection
open to it.
It can achieve this higher perfection with the help of its owner, going beyond its natural
canine capacity.
It is similar with human beings and our relation to God.
We have a human nature, and we can be perfect just as human, by exercising our natural powers
of reason.
We can become wise in science, philosophy, and other fields.
We can become naturally virtuous.
But human nature is also subordinate to the higher Divine nature, so we can also be perfect
as humans-participating-in-the-life-of-God.
This is salvation, and it requires us to go beyond our natural powers of reason, and to
have faith.
With this in mind, we can re-evaluate the first three arguments above.
The first argument for answering "No" began: Salvation is the ultimate perfection of the
human being.
And the perfection of any natural thing should come through its natural abilities.
But faith goes beyond the powers of reason that are part of human nature.
To this we now reply: Since human nature depends on a higher Divine
nature, the fullest possible human perfection requires more than just our natural capacities.
We require supernatural knowledge, which we receive by faith.
In other words, the second premise, "the perfection of any natural thing should come through its
natural abilities," is false.
The second argument for answering "No" began: It is dangerous for anyone to believe what
they do not understand.
If you believe what you do not understand, you might easily believe something that is
actually false.
But matters of faith cannot be clearly understood.
To this we now reply: Just as a virtuous person chooses correctly
because of her virtue, a faithful person believes correctly because of her faith.
God guides her to believe what is true by faith, and to avoid what is false.
In other words, the second premise, "If you believe what you do not understand, you might
easily believe something that is actually false," is false.
The third argument for answering “No" began: The Bible tells us that "the invisible things
of God... are clearly seen."
But whatever is clearly seen can be known, and does not have to be taken on faith.
To this we now reply: Although we can know the invisible things
of God by natural reason, faith shows us the invisible things of God in a higher and clearer way.
In other words, the second premise, "whatever is clearly seen... does not have to be taken
on faith," is false.
That’s the end of my plain-English re-presentation of the arguments from Question 3.
I hope you found it helpful. Thanks for watching today; goodbye.